Tissue visualization and manipulation system

ABSTRACT

A tissue imaging assembly includes a steerable sheath and a steerable catheter deployable within the sheath. The tissue imaging assembly also includes an imaging hood at a distal end of the steerable catheter. The imaging hood is independently translatable with respect to the steerable sheath and the steerable catheter. The steerable catheter includes an imaging element and a lumen for delivering an elongate instrument out a distal region of the steerable catheter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/259,498 filed Oct. 25, 2005, which claims the benefit of priority toU.S. Provisional. Patent. Application. No. 60/649,246 filed Feb. 2,2005, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to medical devices used forvisualizing and/or manipulating regions of tissue within a body. Moreparticularly, the present invention relates to apparatus and methods forvisualizing and/or manipulating tissue regions within a body lumen,e.g., tissue surrounding or adjacent to valves within a heart, which aregenerally difficult to image because of surrounding opaque bodily fluidssuch as blood or the tissue of the inter-atrial septum for trans-septalprocedures.

Conventional devices for visualizing interior regions of a body lumenare known. For example, ultrasound devices have been used to produceimages from within a body in vivo. Ultrasound has been used both withand without contrast agents, which typically enhance ultrasound-derivedimages.

Other conventional methods have utilized catheters or probes havingposition sensors deployed within the body lumen, such as the interior ofa cardiac chamber. These types of positional sensors are typically usedto determine the movement of a cardiac tissue surface or the electricalactivity within the cardiac tissue. When a sufficient number of pointshave been sampled by the sensors, a “map” of the cardiac tissue may begenerated.

Another conventional device utilizes an inflatable balloon which istypically introduced intravascularly in a deflated state and theninflated against the tissue region to be examined. Imaging is typicallyaccomplished by an optical fiber or other apparatus such as electronicchips for viewing the tissue through the membrane(s) of the inflatedballoon. Moreover, the balloon must generally be inflated for imaging.Other conventional balloons utilize a cavity or depression formed at adistal end of the inflated balloon. This cavity or depression is pressedagainst the tissue to be examined and is flushed with a clear fluid toprovide a clear pathway through the blood.

However, such imaging balloons have many inherent disadvantages. Forinstance, such balloons generally require that the balloon be inflatedto a relatively large size which may undesirably displace surroundingtissue and interfere with fine positioning of the imaging system againstthe tissue. Moreover, the working area created by such inflatableballoons are generally cramped and limited in size. Furthermore,inflated balloons may be susceptible to pressure changes in thesurrounding fluid. For example, if the environment surrounding theinflated balloon undergoes pressure changes, e.g., during systolic anddiastolic pressure cycles in a beating heart, the constant pressurechange may affect the inflated balloon volume and its positioning toproduce unsteady or undesirable conditions for optimal tissue imaging.

Accordingly, these types of imaging modalities are generally unable toprovide desirable images useful for sufficient diagnosis and therapy ofthe endoluminal structure, due in part to factors such as dynamic forcesgenerated by the natural movement of the heart. Moreover, anatomicstructures within the body can occlude or obstruct the image acquisitionprocess. Also, the presence and movement of opaque bodily fluids such asblood generally make in vivo imaging of tissue regions within the heartdifficult.

Other external imaging modalities are also conventionally utilized. Forexample, computed tomography (CT) and magnetic resonance imaging (MRI)are typical modalities which are widely used to obtain images of bodylumens such as the interior chambers of the heart. However, such imagingmodalities fail to provide real-time imaging for intra-operativetherapeutic procedures. Fluoroscopic imaging, for instance, is widelyused to identify anatomic landmarks within the heart and other regionsof the body. However, fluoroscopy fails to provide an accurate image ofthe tissue quality or surface and also fails to provide forinstrumentation for performing tissue manipulation or other therapeuticprocedures upon the visualized tissue regions. In addition, fluoroscopyprovides a shadow of the intervening tissue onto a plate or sensor whenit may be desirable to view the intraluminal surface of the tissue todiagnose pathologies or to perform some form of therapy on it.

Thus, a tissue imaging system which is able to provide real-time in vivoimages of tissue regions within body lumens such as the heart throughopaque media such as blood and which also provide instruments fortherapeutic procedures upon the visualized tissue are desirable.

BRIEF SUMMARY OF THE INVENTION

A tissue imaging and manipulation apparatus that may be utilized forprocedures within a body lumen, such as the heart, in whichvisualization of the surrounding tissue is made difficult, if notimpossible, by medium contained within the lumen such as blood, isdescribed below. Generally, such a tissue imaging and manipulationapparatus comprises an optional delivery catheter or sheath throughwhich a deployment catheter and imaging hood may be advanced forplacement against or adjacent to the tissue to be imaged.

The deployment catheter may define a fluid delivery lumen therethroughas well as an imaging lumen within which an optical imaging fiber orassembly may be disposed for imaging tissue. When deployed, the imaginghood may be expanded into any number of shapes, e.g., cylindrical,conical as shown, semi-spherical, etc., provided that an open area orfield is defined by the imaging hood. The open area is the area withinwhich the tissue region of interest may be imaged. The imaging hood mayalso define an atraumatic contact lip or edge for placement or abutmentagainst the tissue region of interest. Moreover, the distal end of thedeployment catheter or separate manipulatable catheters may bearticulated through various controlling mechanisms such as push-pullwires manually or via computer control.

The deployment catheter may also be stabilized relative to the tissuesurface through various methods. For instance, inflatable stabilizingballoons positioned along a length of the catheter may be utilized, ortissue engagement anchors may be passed through or along the deploymentcatheter for temporary engagement of the underlying tissue.

In operation, after the imaging hood has been deployed, fluid may bepumped at a positive pressure through the fluid delivery lumen until thefluid fills the open area completely and displaces any blood from withinthe open area. The fluid may comprise any biocompatible fluid, e.g.,saline, water, plasma, Fluorinert™, etc., which is sufficientlytransparent to allow for relatively undistorted visualization throughthe fluid. The fluid may be pumped continuously or intermittently toallow for image capture by an optional processor which may be incommunication with the assembly.

The imaging hood may be formed into any number of configurations and theimaging assembly may also be utilized with any number of therapeutictools which may be deployed through the deployment catheter.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A shows a side view of one variation of a tissue imaging apparatusduring deployment from a sheath or delivery catheter.

FIG. 1B shows the deployed tissue imaging apparatus of FIG. 1A having anoptionally expandable hood or sheath attached to an imaging and/ordiagnostic catheter.

FIG. 1C shows an end view of a deployed imaging apparatus.

FIGS. 1D to 1F show the apparatus of FIGS. 1A to 1C with an additionallumen, e.g., for passage of a guidewire therethrough.

FIGS. 2A and 2B show one example of a deployed tissue imager positionedagainst or adjacent to the tissue to be imaged and a flow of fluid, suchas saline, displacing blood from within the expandable hood.

FIG. 3A shows an articulatable imaging assembly which may be manipulatedvia push-pull wires or by computer control.

FIGS. 3B and 3C show steerable instruments, respectively, where anarticulatable delivery catheter may be steered within the imaging hoodor a distal portion of the deployment catheter itself may be steered.

FIGS. 4A to 4C show side and cross-sectional end views, respectively, ofanother variation having an off-axis imaging capability.

FIG. 5 shows an illustrative view of an example of a tissue imageradvanced intravascularly within a heart for imaging tissue regionswithin an atrial chamber.

FIGS. 6A to 6C illustrate deployment catheters having one or moreoptional inflatable balloons or anchors for stabilizing the deviceduring a procedure.

FIGS. 7A and 7B illustrate a variation of an anchoring mechanism such asa helical tissue piercing device for temporarily stabilizing the imaginghood relative to a tissue surface.

FIG. 7C shows another variation for anchoring the imaging hood havingone or more tubular support members integrated with the imaging hood,each support members may define a lumen therethrough for advancing ahelical tissue anchor within.

FIG. 8A shows an illustrative example of one variation of how a tissueimager may be utilized with an imaging device.

FIG. 8B shows a further illustration of a hand-held variation of thefluid delivery and tissue manipulation system.

FIGS. 9A to 9C illustrate an example of capturing several images of thetissue at multiple regions.

FIGS. 10A and 10B show charts illustrating how fluid pressure within theimaging hood may be coordinated with the surrounding blood pressure; thefluid pressure in the imaging hood may be coordinated with the bloodpressure or it may be regulated based upon pressure feedback from theblood.

FIG. 11A shows a side view of another variation of a tissue imagerhaving an imaging balloon within an expandable hood.

FIG. 11B shows another variation of a tissue imager utilizing atranslucent or transparent imaging balloon.

FIG. 12A shows another variation in which a flexible expandable ordistensible membrane may be incorporated within the imaging hood toalter the volume of fluid dispensed.

FIGS. 12B and 12C show another variation in which the imaging hood maybe partially or selectively deployed from the catheter to alter the areaof the tissue being visualized as well as the volume of the dispensedfluid.

FIGS. 13A and 13B show exemplary side and cross-sectional views,respectively, of another variation in which the injected fluid may bedrawn back into the device for minimizing fluid input into a body beingtreated.

FIGS. 14A to 14D show various configurations and methods for configuringan imaging hood into a low-profile for delivery and/or deployment.

FIGS. 15A and 15B show an imaging hood having an helically expandingframe or support.

FIGS. 16A and 16B show another imaging hood having one or more hoodsupport members, which are pivotably attached at their proximal ends todeployment catheter, integrated with a hood membrane.

FIGS. 17A and 17B show yet another variation of the imaging hood havingat least two or more longitudinally positioned support memberssupporting the imaging hood membrane where the support members aremovable relative to one another via a torquing or pulling or pushingforce.

FIGS. 18A and 18B show another variation where a distal portion of thedeployment catheter may have several pivoting members which form atubular shape in its low profile configuration.

FIGS. 19A and 19B show another variation where the distal portion ofdeployment catheter may be fabricated from a flexible metallic orpolymeric material to form a radially expanding hood.

FIGS. 20A and 20B show another variation where the imaging hood may beformed from a plurality of overlapping hood members which overlie oneanother in an overlapping pattern.

FIGS. 21A and 21B show another example of an expandable hood which ishighly conformable against tissue anatomy with varying geography.

FIG. 22A shows yet another example of an expandable hood having a numberof optional electrodes placed about the contact edge or lip of the hoodfor sensing tissue contact or detecting arrhythmias.

FIG. 22B shows another variation for conforming the imaging hood againstthe underlying tissue where an inflatable contact edge may be disposedaround the circumference of the imaging hood.

FIG. 23 shows a variation of the system which may be instrumented with atransducer for detecting the presence of blood seeping back into theimaging hood.

FIGS. 24A and 24B show variations of the imaging hood instrumented withsensors for detecting various physical parameters; the sensors may beinstrumented around the outer surface of the imaging hood and alsowithin the imaging hood.

FIGS. 25A and 25B show a variation where the imaging hood may have oneor more LEDs over the hood itself for providing illumination of thetissue to be visualized.

FIGS. 26A and 26B show another variation in which a separateillumination tool having one or more LEDs mounted thereon may beutilized within the imaging hood.

FIG. 27 shows one example of how a therapeutic tool may be advancedthrough the tissue imager for treating a tissue region of interest.

FIG. 28 shows another example of a helical therapeutic tool for treatingthe tissue region of interest.

FIG. 29 shows a variation of how a therapeutic tool may be utilized withan expandable imaging balloon.

FIGS. 30A and 30B show alternative configurations for therapeuticinstruments which may be utilized; one variation is shown having anangled instrument arm and another variation is shown with an off-axisinstrument arm.

FIGS. 31A to 31C show side and end views, respectively, of an imagingsystem which may be utilized with an ablation probe.

FIGS. 32A and 32B show side and end views, respectively, of anothervariation of the imaging hood with an ablation probe, where the imaginghood may be enclosed for regulating a temperature of the underlyingtissue.

FIGS. 33A and 33B show an example in which the imaging fluid itself maybe altered in temperature to facilitate various procedures upon theunderlying tissue.

FIGS. 34A and 34B show an example of a laser ring generator which may beutilized with the imaging system and an example for applying the laserring generator within the left atrium of a heart for treating atrialfibrillation.

FIGS. 35A to 35C show an example of an extendible cannula generallycomprising an elongate tubular member which may be positioned within thedeployment catheter during delivery and then projected distally throughthe imaging hood and optionally beyond.

FIGS. 36A and 36B show side and end views, respectively, of an imaginghood having one or more tubular support members integrated with the hoodfor passing instruments or tools therethrough for treatment upon theunderlying tissue.

FIGS. 37A and 37B illustrate how an imaging device may be guided withina heart chamber to a region of interest utilizing a lighted probepositioned temporarily within, e.g., a lumen of the coronary sinus.

FIGS. 38A and 38B show an imaging hood having a removable disk-shapedmember for implantation upon the tissue surface.

FIGS. 39A to 39C show one method for implanting the removable disk ofFIGS. 38A and 38B.

FIGS. 40A and 40B illustrate an imaging hood having a deployable anchorassembly attached to the tissue contact edge and an assembly view of theanchors and the suture or wire connected to the anchors, respectively.

FIGS. 41A to 41D show one method for deploying the anchor assembly ofFIGS. 40A and 40B for closing an opening or wound.

FIG. 42 shows another variation in which the imaging system may befluidly coupled to a dialysis unit for filtering a patient's blood.

FIGS. 43A and 43B show a variation of the deployment catheter having afirst deployable hood and a second deployable hood positioned distal tothe first hood; the deployment catheter may also have a side-viewingimaging element positioned between the first and second hoods forimaging tissue between the expanded hoods.

FIGS. 44A and 44D show side and end views, respectively, of a deploymentcatheter having a side-imaging balloon in an un-inflated low-profileconfiguration.

FIGS. 45A to 45C show side, top, and end views, respectively, of theinflated balloon of FIGS. 44A and 44B defining a visualization field inthe inflated balloon.

FIGS. 46A and 46B show side and cross-sectional end views, respectively,for one method of use in visualizing a lesion upon a vessel wall withinthe visualization field of the inflated balloon from FIGS. 45A to 45C.

DETAILED DESCRIPTION OF THE INVENTION

A tissue-imaging and manipulation apparatus described below is able toprovide real-time images in vivo of tissue regions within a body lumensuch as a heart, which is filled with blood flowing dynamicallytherethrough and is also able to provide intravascular tools andinstruments for performing various procedures upon the imaged tissueregions. Such an apparatus may be utilized for many procedures, e.g.,facilitating trans-septal access to the left atrium, cannulating thecoronary sinus, diagnosis of valve regurgitation/stenosis,valvuloplasty, atrial appendage closure, arrhythmogenic focus ablation,among other procedures.

One variation of a tissue access and imaging apparatus is shown in thedetail perspective views of FIGS. 1A to 1C. As shown in FIG. 1A, tissueimaging and manipulation assembly 10 may be delivered intravascularlythrough the patient's body in a low-profile configuration via a deliverycatheter or sheath 14. In the case of treating tissue, such as themitral valve located at the outflow tract of the left atrium of theheart, it is generally desirable to enter or access the left atriumwhile minimizing trauma to the patient. To non-operatively effect suchaccess, one conventional approach involves puncturing the intra-atrialseptum from the right atrial chamber to the left atrial chamber in aprocedure commonly called a trans-septal procedure or septostomy. Forprocedures such as percutaneous valve repair and replacement,trans-sepal access to the left atrial chamber of the heart may allow forlarger devices to be introduced into the venous system than cangenerally be introduced percutaneously into the arterial system.

When the imaging and manipulation assembly 10 is ready to be utilizedfor imaging tissue, imaging hood 12 may be advanced relative to catheter14 and deployed from a distal opening of catheter 14, as shown by thearrow. Upon deployment, imaging hood 12 may be unconstrained to expandor open into a deployed imaging configuration, as shown in FIG. 1B.Imaging hood 12 may be fabricated from a variety of pliable orconformable biocompatible material including but not limited to, e.g.,polymeric, plastic, or woven materials. One example of a woven materialis Kevlar® (E. I. du Pont de Nemours, Wilmington, Del.), which is anaramid and which can be made into thin, e.g., less than 0.001 in.,materials which maintain enough integrity for such applicationsdescribed herein. Moreover, the imaging hood 12 may be fabricated from atranslucent or opaque material and in a variety of different colors tooptimize or attenuate any reflected lighting from surrounding fluids orstructures, i.e., anatomical or mechanical structures or instruments. Ineither case, imaging hood 12 may be fabricated into a uniform structureor a scaffold-supported structure, in which case a scaffold made of ashape memory alloy, such as Nitinol, or a spring steel, or plastic,etc., may be fabricated and covered with the polymeric, plastic, orwoven material.

Imaging hood 12 may be attached at interface 24 to a deployment catheter16 which may be translated independently of deployment catheter orsheath 14. Attachment of interface 24 may be accomplished through anynumber of conventional methods. Deployment catheter 16 may define afluid delivery lumen 18 as well as an imaging lumen 20 within which anoptical imaging fiber or assembly may be disposed for imaging tissue.When deployed, imaging hood 12 may expand into any number of shapes,e.g., cylindrical, conical as shown, semi-spherical, etc., provided thatan open area or field 26 is defined by imaging hood 12. The open area 26is the area within which the tissue region of interest may be imaged.Imaging hood 12 may also define an atraumatic contact lip or edge 22 forplacement or abutment against the tissue region of interest. Moreover,the diameter of imaging hood 12 at its maximum fully deployed diameter,e.g., at contact lip or edge 22, is typically greater relative to adiameter of the deployment catheter 16 (although a diameter of contactlip or edge 22 may be made to have a smaller or equal diameter ofdeployment catheter 16). For instance, the contact edge diameter mayrange anywhere from 1 to 5 times (or even greater, as practicable) adiameter of deployment catheter 16. FIG. 1C shows an end view of theimaging hood 12 in its deployed configuration. Also shown are thecontact lip or edge 22 and fluid delivery lumen 18 and imaging lumen 20.

The imaging and manipulation assembly 10 may additionally define aguidewire lumen therethrough, e.g., a concentric or eccentric lumen, asshown in the side and end views, respectively, of FIGS. 1D to 1F. Thedeployment catheter 16 may define guidewire lumen 19 for facilitatingthe passage of the system over or along a guidewire 17, which may beadvanced intravascularly within a body lumen. The deployment catheter 16may then be advanced over the guidewire 17, as generally known in thean.

During operation, after imaging hood 12 has been deployed, as in FIG.1B, and desirably positioned against the tissue region to be imagedalong contact edge 22, the displacing fluid may be pumped at positivepressure through fluid delivery lumen 18 until the fluid fills open area26 completely and displaces any fluid 28 from within open area 26. Thedisplacing fluid flow may be laminarized to improve its clearing effectand to help prevent blood from re-entering the imaging hood 12.Alternatively, fluid flow may be started before the deployment takesplace. The displacing fluid, also described herein as imaging fluid, maycomprise any biocompatible fluid, e.g., saline, water, plasma, etc.,which is sufficiently transparent to allow for relatively undistortedvisualization through the fluid. Alternatively or additionally, anynumber of therapeutic drugs may be suspended within the fluid or maycomprise the fluid itself which is pumped into open area 26 and which issubsequently passed into and through the heart and the patient body.

As seen in the example of FIGS. 2A and 2B, deployment catheter 16 may bemanipulated to position deployed imaging hood 12 against or near theunderlying tissue region of interest to be imaged, in this example aportion of annulus A of mitral valve MV within the left atrial chamber.As the surrounding blood 30 flows around imaging hood 12 and within openarea 26 defined within imaging hood 12, as seen in FIG. 2A, theunderlying annulus A is obstructed by the opaque blood 30 and isdifficult to view through the imaging lumen 20. The translucent fluid28, such as saline, may then be pumped through fluid delivery lumen 18,intermittently or continuously, until the blood 30 is at leastpartially, and preferably completely, displaced from within open area 26by fluid 28, as shown in FIG. 2B.

Although contact edge 22 need not directly contact the underlyingtissue, it is at least preferably brought into close proximity to thetissue such that the flow of clear fluid 28 from open area 26 may bemaintained to inhibit significant backflow of blood 30 back into openarea 26. Contact edge 22 may also be made of a soft elastomeric materialsuch as certain soft grades of silicone or polyurethane, as typicallyknown, to help contact edge 22 conform to an uneven or rough underlyinganatomical tissue surface. Once the blood 30 has been displaced fromimaging hood 12, an image may then be viewed of the underlying tissuethrough the clear fluid 30. This image may then be recorded or availablefor real-time viewing for performing a therapeutic procedure. Thepositive flow of fluid 28 may be maintained continuously to provide forclear viewing of the underlying tissue. Alternatively, the fluid 28 maybe pumped temporarily or sporadically only until a clear view of thetissue is available to be imaged and recorded, at which point the fluidflow 28 may cease and blood 30 may be allowed to seep or flow back intoimaging hood 12. This process may be repeated a number of times at thesame tissue region or at multiple tissue regions.

In desirably positioning the assembly at various regions within thepatient body, a number of articulation and manipulation controls may beutilized. For example, as shown in the articulatable imaging assembly 40in FIG. 3A, one or more push-pull wires 42 may be routed throughdeployment catheter 16 for steering the distal end portion of the devicein various directions 46 to desirably position the imaging hood 12adjacent to a region of tissue to be visualized. Depending upon thepositioning and the number of push-pull wires 42 utilized, deploymentcatheter 16 and imaging hood 12 may be articulated into any number ofconfigurations 44. The push-pull wire or wires 42 may be articulated viatheir proximal ends from outside the patient body manually utilizing oneor more controls. Alternatively, deployment catheter 16 may bearticulated by computer control, as further described below.

Additionally or alternatively, an articulatable delivery catheter 48,which may be articulated via one or more push-pull wires and having animaging lumen and one or more working lumens, may be delivered throughthe deployment catheter 16 and into imaging hood 12. With a distalportion of articulatable delivery catheter 48 within imaging hood 12,the clear displacing fluid may be pumped through delivery catheter 48 ordeployment catheter 16 to clear the field within imaging hood 12. Asshown in FIG. 3B, the articulatable delivery catheter 48 may bearticulated within the imaging hood to obtain a better image of tissueadjacent to the imaging hood 12. Moreover, articulatable deliverycatheter 48 may be articulated to direct an instrument or tool passedthrough the catheter 48, as described in detail below, to specific areasof tissue imaged through imaging hood 12 without having to repositiondeployment catheter 16 and re-clear the imaging field within hood 12.

Alternatively, rather than passing an articulatable delivery catheter 48through the deployment catheter 16, a distal portion of the deploymentcatheter 16 itself may comprise a distal end 49 which is articulatablewithin imaging hood 12, as shown in FIG. 3C. Directed imaging,instrument delivery, etc., may be accomplished directly through one ormore lumens within deployment catheter 16 to specific regions of theunderlying tissue imaged within imaging hood 12.

Visualization within the imaging hood 12 may be accomplished through animaging lumen 20 defined through deployment catheter 16, as describedabove. In such a configuration, visualization is available in astraight-line manner, i.e., images are generated from the field distallyalong a longitudinal axis defined by the deployment catheter 16.Alternatively or additionally, an articulatable imaging assembly havinga pivotable support member 50 may be connected to, mounted to, orotherwise passed through deployment catheter 16 to provide forvisualization off-axis relative to the longitudinal axis defined bydeployment catheter 16, as shown in FIG. 4A. Support member 50 may havean imaging element 52, e.g., a CCD or CMOS imager or optical fiber,attached at its distal end with its proximal end connected to deploymentcatheter 16 via a pivoting connection 54.

If one or more optical fibers are utilized for imaging, the opticalfibers 58 may be passed through deployment catheter 16, as shown in thecross-section of FIG. 4B, and routed through the support member 50. Theuse of optical fibers 58 may provide for increased diameter sizes of theone or several lumens 56 through deployment catheter 16 for the passageof diagnostic and/or therapeutic tools therethrough. Alternatively,electronic chips, such as a charge coupled device (CCD) or a CMOSimager, which are typically known, may be utilized in place of theoptical fibers 58, in which case the electronic imager may be positionedin the distal portion of the deployment catheter 16 with electric wiresbeing routed proximally through the deployment catheter 16.Alternatively, the electronic imagers may be wirelessly coupled to areceiver for the wireless transmission of images. Additional opticalfibers or light emitting diodes (LEDs) can be used to provide lightingfor the image or operative theater, as described below in furtherdetail. Support member 50 may be pivoted via connection 54 such that themember 50 can be positioned in a low-profile configuration withinchannel or groove 60 defined in a distal portion of catheter 16, asshown in the cross-section of FIG. 4C. During intravascular delivery ofdeployment catheter 16 through the patient body, support member 50 canbe positioned within channel or groove 60 with imaging hood 12 also inits low-profile configuration. During visualization, imaging hood 12 maybe expanded into its deployed configuration and support member 50 may bedeployed into its off-axis configuration for imaging the tissue adjacentto hood 12, as in FIG. 4A. Other configurations for support member 50for off-axis visualization may be utilized, as desired.

FIG. 5 shows an illustrative cross-sectional view of a heart H havingtissue regions of interest being viewed via an imaging assembly 10. Inthis example, delivery catheter assembly 70 may be introducedpercutaneously into the patient's vasculature and advanced through thesuperior vena cava SVC and into the right atrium RA. The deliverycatheter or sheath 72 may be articulated through the atrial septum ASand into the left atrium LA for viewing or treating the tissue, e.g.,the annulus A, surrounding the mitral valve MV. As shown, deploymentcatheter 16 and imaging hood 12 may be advanced out of delivery catheter72 and brought into contact or in proximity to the tissue region ofinterest. In other examples, delivery catheter assembly 70 may beadvanced through the inferior vena cava IVC, if so desired. Moreover,other regions of the heart H, e.g., the right ventricle RV or leftventricle LV, may also be accessed and imaged or treated by imagingassembly 10.

In accessing regions of the heart H or other parts of the body, thedelivery catheter or sheath 14 may comprise a conventionalintra-vascular catheter or an endoluminal delivery device.Alternatively, robotically-controlled delivery catheters may also beoptionally utilized with the imaging assembly described herein, in whichcase a computer-controller 74 may be used to control the articulationand positioning of the delivery catheter 14. An example of arobotically-controlled delivery catheter which may be utilized isdescribed in further detail in U.S. Pat. Pub. 2002/0087169 A1 to Brocket al. entitled “Flexible Instrument”, which is incorporated herein byreference in its entirety. Other robotically-controlled deliverycatheters manufactured by Hansen Medical. Inc. (Mountain View, Calif.)may also be utilized with the delivery catheter 14.

To facilitate stabilization of the deployment catheter 16 during aprocedure, one or more inflatable balloons or anchors 76 may bepositioned along the length of catheter 16, as shown in FIG. 6A. Forexample, when utilizing a trans-septal approach across the atrial septumAS into the left atrium LA, the inflatable balloons 76 may be inflatedfrom a low-profile into their expanded configuration to temporarilyanchor or stabilize the catheter 16 position relative to the heart H.FIG. 6B shows a first balloon 78 inflated while FIG. 6C also shows asecond balloon 80 inflated proximal to the first balloon 78. In such aconfiguration, the septal wall AS may be wedged or sandwiched betweenthe balloons 78, 80 to temporarily stabilize the catheter 16 and imaginghood 12. A single balloon 78 or both balloons 78, 80 may be used. Otheralternatives may utilize expandable mesh members, malecots, or any othertemporary expandable structure. After a procedure has been accomplished,the balloon assembly 76 may be deflated or re-configured into alow-profile for removal of the deployment catheter 16.

To further stabilize a position of the imaging hood 12 relative to atissue surface to be imaged, various anchoring mechanisms may beoptionally employed for temporarily holding the imaging hood 12 againstthe tissue. Such anchoring mechanisms may be particularly useful forimaging tissue which is subject to movement, e.g., when imaging tissuewithin the chambers of a beating heart. A tool delivery catheter 82having at least one instrument lumen and an optional visualization lumenmay be delivered through deployment catheter 16 and into an expandedimaging hood 12. As the imaging hood 12 is brought into contact againsta tissue surface T to be examined, an anchoring mechanisms such as ahelical tissue piercing device 84 may be passed through the tooldelivery catheter 82, as shown in FIG. 7A, and into imaging hood 12.

The helical tissue engaging device 84 may be torqued from its proximalend outside the patient body to temporarily anchor itself into theunderlying tissue surface T. Once embedded within the tissue T, thehelical tissue engaging device 84 may be pulled proximally relative todeployment catheter 16 while the deployment catheter 16 and imaging hood12 are pushed distally, as indicated by the arrows in FIG. 7B, to gentlyforce the contact edge or lip 22 of imaging hood against the tissue T.The positioning of the tissue engaging device 84 may be lockedtemporarily relative to the deployment catheter 16 to ensure securepositioning of the imaging hood 12 during a diagnostic or therapeuticprocedure within the imaging hood 12. After a procedure, tissue engagingdevice 84 may be disengaged from the tissue by torquing its proximal endin the opposite direction to remove the anchor form the tissue T and thedeployment catheter 16 may be repositioned to another region of tissuewhere the anchoring process may be repeated or removed from the patientbody. The tissue engaging device 84 may also be constructed from otherknown tissue engaging devices such as vacuum-assisted engagement orgrasper-assisted engagement tools, among others.

Although a helical anchor 84 is shown, this is intended to beillustrative and other types of temporary anchors may be utilized, e.g.,hooked or barbed anchors, graspers, etc. Moreover, the tool deliverycatheter 82 may be omitted entirely and the anchoring device may bedelivered directly through a lumen defined through the deploymentcatheter 16.

In another variation where the tool delivery catheter 82 may be omittedentirely to temporarily anchor imaging hood 12, FIG. 7C shows an imaginghood 12 having one or more tubular support members 86, e.g. four supportmembers 86 as shown, integrated with the imaging hood 12. The tubularsupport members 86 may define lumens therethrough each having helicaltissue engaging devices 88 positioned within. When an expanded imaginghood 12 is to be temporarily anchored to the tissue, the helical tissueengaging devices 88 may be urged distally to extend from imaging hood 12and each may be torqued from its proximal end to engage the underlyingtissue T. Each of the helical tissue engaging devices 88 may be advancedthrough the length of deployment catheter 16 or they may be positionedwithin tubular support members 86 during the delivery and deployment ofimaging hood 12. Once the procedure within-imaging hood 12 is finished,each of the tissue engaging devices 88 may be disengaged from the tissueand the imaging hood 12 may be repositioned to another region of tissueor removed from the patient body.

An illustrative example is shown in FIG. 8A of a tissue imaging assemblyconnected to a fluid delivery system 90 and to an optional processor 98and image recorder and/or viewer 100. The fluid delivery system 90 maygenerally comprise a pump 92 and an optional valve 94 for controllingthe flow rate of the fluid into the system. A fluid reservoir 96,fluidly connected to pump 92, may hold the fluid to be pumped throughimaging hood 12. An optional central processing unit or processor 98 maybe in electrical communication with fluid delivery system 90 forcontrolling flow parameters such as the flow rate and/or velocity of thepumped fluid. The processor 98 may also be in electrical communicationwith an image recorder and/or viewer 100 for directly viewing the imagesof tissue received from within imaging hood 12. Imager recorder and/orviewer 100 may also be used not only to record the image but also thelocation of the viewed tissue region, if so desired.

Optionally, processor 98 may also be utilized to coordinate the fluidflow and the image capture. For instance, processor 98 may be programmedto provide for fluid flow from reservoir 96 until the tissue area hasbeen displaced of blood to obtain a clear image. Once the image has beendetermined to be sufficiently clear, either visually by a practitioneror by computer, an image of the tissue may be captured automatically byrecorder 100 and pump 92 may be automatically stopped or slowed byprocessor 98 to cease the fluid flow into the patient. Other variationsfor fluid delivery and image capture are, of course, possible and theaforementioned configuration is intended only to be illustrative and notlimiting.

FIG. 8B shows a further illustration of a hand-held variation of thefluid delivery and tissue manipulation system 110. In this variation,system 110 may have a housing or handle assembly 112 which can be heldor manipulated by the physician from outside the patient body. The fluidreservoir 114, shown in this variation as a syringe, can be fluidlycoupled to the handle assembly 112 and actuated via a pumping mechanism116, e.g., lead screw. Fluid reservoir 114 may be a simple reservoirseparated from the handle assembly 112 and fluidly coupled to handleassembly 112 via one or more tubes. The fluid flow rate and othermechanisms may be metered by the electronic controller 118.

Deployment of imaging hood 12 may be actuated by a hood deploymentswitch 120 located on the handle assembly 112 while dispensation of thefluid from reservoir 114 may be actuated by a fluid deployment switch122, which can be electrically coupled to the controller 118. Controller118 may also be electrically coupled to a wired or wireless antenna 124optionally integrated with the handle assembly 112, as shown in thefigure. The wireless antenna 124 can be used to wirelessly transmitimages captured from the imaging hood 12 to a receiver, e.g., viaBluetooth® wireless technology (Bluetooth SIG. Inc., Bellevue, Wash.),RF, etc., for viewing on a monitor 128 or for recording for laterviewing.

Articulation control of the deployment catheter 16, or a deliverycatheter or sheath 14 through which the deployment catheter 16 may bedelivered, may be accomplished by computer control, as described above,in which case an additional controller may be utilized with handleassembly 112. In the case of manual articulation, handle assembly 112may incorporate one or more articulation controls 126 for manualmanipulation of the position of deployment catheter 16. Handle assembly112 may also define one or more instrument ports 130 through which anumber of intravascular tools may be passed for tissue manipulation andtreatment within imaging hood 12, as described further below.Furthermore, in certain procedures, fluid or debris may be sucked intoimaging hood 12 for evacuation from the patient body by optionallyfluidly coupling a suction pump 132 to handle assembly 112 or directlyto deployment catheter 16.

As described above, fluid may be pumped continuously into imaging hood12 to provide for clear viewing of the underlying tissue. Alternatively,fluid may be pumped temporarily or sporadically only until a clear viewof the tissue is available to be imaged and recorded, at which point thefluid flow may cease and the blood may be allowed to seep or flow backinto imaging hood 12. FIGS. 9A to 9C illustrate an example of capturingseveral images of the tissue at multiple regions. Deployment catheter 16may be desirably positioned and imaging hood 12 deployed and broughtinto position against a region of tissue to be imaged, in this examplethe tissue surrounding a mitral valve MV within the left atrium of apatient's heart. The imaging hood 12 may be optionally anchored to thetissue, as described above, and then cleared by pumping the imagingfluid into the hood 12. Once sufficiently clear, the tissue may bevisualized and the image captured by control electronics 118. The firstcaptured image 140 may be stored and/or transmitted wirelessly 124 to amonitor 128 for viewing by the physician, as shown in FIG. 9A.

The deployment catheter 16 may be then repositioned to an adjacentportion of mitral valve MV, as shown in FIG. 9B, where the process maybe repeated to capture a second image 142 for viewing and/or recording.The deployment catheter 16 may again be repositioned to another regionof tissue, as shown in FIG. 9C, where a third image 144 may be capturedfor viewing and/or recording. This procedure may be repeated as manytimes as necessary for capturing a comprehensive image of the tissuesurrounding mitral valve MV, or any other tissue region. When thedeployment catheter 16 and imaging hood 12 is repositioned from tissueregion to tissue region, the pump may be stopped during positioning andblood or surrounding fluid may be allowed to enter within imaging hood12 until the tissue is to be imaged, where the imaging hood 12 may becleared, as above.

As mentioned above, when the imaging hood 12 is cleared by pumping theimaging fluid within for clearing the blood or other bodily fluid, thefluid may be pumped continuously to maintain the imaging fluid withinthe hood 12 at a positive pressure or it may be pumped under computercontrol for slowing or stopping the fluid flow into the hood 12 upondetection of various parameters or until a clear image of the underlyingtissue is obtained. The control electronics 118 may also be programmedto coordinate the fluid flow into the imaging hood 12 with variousphysical parameters to maintain a clear image within imaging hood 12.

One example is shown in FIG. 10A which shows a chart 150 illustratinghow fluid pressure within die imaging hood 12 may be coordinated withthe surrounding blood pressure. Chart 150 shows the cyclical bloodpressure 156 alternating between diastolic pressure 152 and systolicpressure 154 over time T due to the beating motion of the patient heart.The fluid pressure of the imaging fluid, indicated by plot 160, withinimaging hood 12 may be automatically timed to correspond to the bloodpressure changes 160 such that an increased pressure is maintainedwithin imaging hood 12 which is consistently above the blood pressure156 by a slight increase ΔP, as illustrated by the pressure differenceat the peak systolic pressure 158. This pressure difference, .ΔP, may bemaintained within imaging hood 12 over the pressure variance of thesurrounding blood pressure to maintain a positive imaging fluid pressurewithin imaging hood 12 to maintain a clear view of the underlyingtissue. One benefit of maintaining a constant .ΔP is a constant flow andmaintenance of a clear field

FIG. 10B shows a chart 162 illustrating another variation formaintaining a clear view of the underlying tissue where one or moresensors within the imaging hood 12, as described in further detailbelow, may be configured to sense pressure changes within the imaginghood 12 and to correspondingly increase the imaging fluid pressurewithin imaging hood 12. This may result in a time delay, .ΔT, asillustrated by the shifted fluid pressure 160 relative to the cyclingblood pressure 156, although the time delay .ΔT may be negligible inmaintaining the clear image of the underlying tissue. Predictivesoftware algorithms can also be used to substantially eliminate thistime delay by predicting when the next pressure wave peak will arriveand by increasing the pressure ahead of die pressure wave's arrival byan amount of time equal to the aforementioned time delay to essentiallycancel the time delay out.

The variations in fluid pressure within imaging hood 12 may beaccomplished in part due to the nature of imaging hood 12. An inflatableballoon, which is conventionally utilized for imaging tissue, may beaffected by the surrounding blood pressure changes. On the other hand,an imaging hood 12 retains a constant volume therewithin and isstructurally unaffected by the surrounding blood pressure changes, thusallowing for pressure increases therewithin. The material that hood 12is made from may also contribute to the manner in which the pressure ismodulated within this hood 12. A stiffer hood material, such as highdurometer polyurethane or Nylon, may facilitate the maintaining of anopen hood when deployed. On the other hand, a relatively lower durometeror softer material, such as a low durometer PVC or polyurethane, maycollapse from the surrounding fluid pressure and may not adequatelymaintain a deployed or expanded hood.

Turning now to the imaging hood, other variations of the tissue imagingassembly may be utilized, as shown in FIG. 11A, which shows anothervariation comprising an additional imaging balloon 172 within an imaginghood 174. In this variation, an expandable balloon 172 having atranslucent skin may be positioned within imaging hood 174. Balloon 172may be made from any distensible biocompatible material havingsufficient translucent properties which allow for visualizationtherethrough. Once the imaging hood 174 has been deployed against thetissue region of interest, balloon 172 may be filled with a fluid, suchas saline, or less preferably a gas, until balloon 172 has been expandeduntil the blood has been sufficiently displaced. The balloon 172 maythis be expanded proximal to or into contact against the tissue regionto be viewed. The balloon 172 can also be filled with contrast media toallow it to be viewed on fluoroscopy to aid in its positioning. Theimager, e.g., fiber optic, positioned within deployment catheter 170 maythen be utilized to view the tissue region through the balloon 172 andany additional fluid which may be pumped into imaging hood 174 via oneor more optional fluid ports 176, which may be positioned proximally ofballoon 172 along a portion of deployment catheter 170. Alternatively,balloon 172 may define one or more holes over its surface which allowfor seepage or passage of the fluid contained therein to escape anddisplace the blood from within imaging hood 174.

FIG. 11B shows another alternative in which balloon 180 may be utilizedalone. Balloon 180, attached to deployment catheter 178, may be filledwith fluid, such as saline or contrast media, and is preferably allowedto come into direct contact with the tissue region to be imaged.

FIG. 12A shows another alternative in which deployment catheter 16incorporates imaging hood 12, as above, and includes an additionalflexible membrane 182 within imaging hood 12. Flexible membrane 182 maybe attached at a distal end of catheter 16 and optionally at contactedge 22. Imaging hood 12 may be utilized, as above, and membrane 182 maybe deployed from catheter 16 in vivo or prior to placing catheter 16within a patient to reduce the volume within imaging hood 12. The volumemay be reduced or minimized to reduce the amount of fluid dispensed forvisualization or simply be to reduced depending upon the area of tissueto be visualized.

FIGS. 12B and 12C show yet another alternative in which imaging hood 186may be withdrawn proximally within deployment catheter 184 or deployeddistally from catheter 186, as shown, to vary the volume of imaging hood186 and thus the volume of dispensed fluid. Imaging hood 186 may be seenin FIG. 12B as being partially deployed from, e.g., a circumferentiallydefined lumen within catheter 184, such as annular lumen 188. Theunderlying tissue may be visualized with imaging hood 186 only partiallydeployed. Alternatively, imaging hood 186′ may be fully deployed, asshown in FIG. 12C, by urging hood 186′ distally out from annular lumen188. In this expanded configuration, the area of tissue to be visualizedmay be increased as hood 186′ is expanded circumferentially.

FIGS. 13A and 13B show perspective and cross-sectional side views,respectively, of yet another variation of imaging assembly which mayutilize a fluid suction system for minimizing the amount of fluidinjected into the patient's heart or other body lumen during tissuevisualization. Deployment catheter 190 in this variation may define aninner tubular member 196 which may be integrated with deploymentcatheter 190 or independently translatable. Fluid delivery lumen 198defined through member 196 may be fluidly connected to imaging hood 192,which may also define one or more open channels 194 over its contact lipregion. Fluid pumped through fluid delivery lumen 198 may thus fill openarea 202 to displace any blood or other fluids or objects therewithin.As the clear fluid is forced out of open area 202, it may be sucked ordrawn immediately through one or more channels 194 and back intodeployment catheter 190. Tubular member 196 may also define one or moreadditional working channels 200 for the passage of any tools orvisualization devices.

In deploying the imaging hood in the examples described herein, theimaging hood may take on any number of configurations when positioned orconfigured for a low-profile delivery within the delivery catheter, asshown in the examples of FIGS. 14A to 14D. These examples are intendedto be illustrative and are not intended to be limiting in scope. FIG.14A shows one example in which imaging hood 212 may be compressed withincatheter 210 by folding hood 212 along a plurality of pleats. Hood 212may also comprise scaffolding or frame 214 made of a super-elastic orshape memory material or alloy, e.g., Nitinol, Elgiloy, shape memorypolymers, electroactive polymers, or a spring stainless steel. The shapememory material may act to expand or deploy imaging hood 212 into itsexpanded configuration when urged in the direction of the arrow from theconstraints of catheter 210.

FIG. 14B shows another example in which imaging hood 216 may be expandedor deployed from catheter 210 from a folded and overlappingconfiguration. Frame or scaffolding 214 may also be utilized in thisexample. FIG. 14C shows yet another example in which imaging hood 218may be rolled, inverted, or everted upon itself for deployment. In yetanother example, FIG. 14D shows a configuration in which imaging hood220 may be fabricated from an extremely compliant material which allowsfor hood 220 to be simply compressed into a low-profile shape. From thislow-profile compressed shape, simply releasing hood 220 may allow for itto expand into its deployed configuration, especially if a scaffold orframe of a shape memory or superelastic material, e.g., Nitinol, isutilized in its construction.

Another variation for expanding the imaging hood is shown in FIGS. 15Aand 15B which illustrates an helically expanding frame or support 230.In its constrained low-profile configuration, shown in FIG. 15A, helicalframe 230 may be integrated with the imaging hood 12 membrane. When freeto expand, as shown in FIG. 15B, helical frame 230 may expand into aconical or tapered shape. Helical frame 230 may alternatively be madeout of heat-activated Nitinol to allow it to expand upon application ofa current.

FIGS. 16A and 16B show yet another variation in which imaging hood 12may comprise one or more hood support members 232 integrated with thehood membrane. These longitudinally attached support members 232 may bepivotably attached at their proximal ends to deployment catheter 16. Oneor more pullwires 234 may be routed through the length of deploymentcatheter 16 and extend through one or more openings 238 defined indeployment catheter 16 proximally to imaging hood 12 into attachmentwith a corresponding support member 232 at a pullwire attachment point236. The support members 232 may be fabricated from a plastic or metal,such as stainless steel. Alternatively, the support members 232 may bemade from a superelastic or shape memory alloy, such as Nitinol, whichmay self-expand into its deployed configuration without the use or needof pullwires. A heat-activated Nitinol may also be used which expandsupon the application of thermal energy or electrical energy. In anotheralternative, support members 232 may also be constructed as inflatablelumens utilizing, e.g., PET balloons. From its low-profile deliveryconfiguration shown in FIG. 16A, the one or more pullwires 234 may betensioned from their proximal ends outside the patient body to pull acorresponding support member 232 into a deployed configuration, as shownin FIG. 16B, to expand imaging hood 12. To reconfigure imaging hood 12back into its low profile, deployment catheter 16 may be pulledproximally into a constraining catheter or the pullwires 234 may besimply pushed distally to collapse imaging hood 12.

FIGS. 17A and 17B show yet another variation of imaging hood 240 havingat least two or more longitudinally positioned support members 242supporting the imaging hood membrane. The support members 242 each havecross-support members 244 which extend diagonally between and arepivotably attached to the support members 242. Each of the cross-supportmembers 244 may be pivotably attached to one another where theyintersect between the support members 242. A jack or screw member 246may be coupled to each cross-support member 244 at this intersectionpoint and a torquing member, such as a torqueable wire 248, may becoupled to each jack or screw member 246 and extend proximally throughdeployment catheter 16 to outside the patient body. From outside thepatient body, the torqueable wires 248 may be torqued to turn the jackor screw member 246 which in turn urges the cross-support members 244 toangle relative to one another and thereby urge the support members 242away from one another. Thus, the imaging hood 240 may be transitionedfrom its low-profile, shown in FIG. 17A, to its expanded profile, shownin FIG. 17B, and back into its low-profile by torquing wires 248.

FIGS. 18A and 18B show yet another variation on the imaging hood and itsdeployment. As shown, a distal portion of deployment catheter 16 mayhave several pivoting members 250, e.g., two to four sections, whichform a tubular shape in its low profile configuration, as shown in FIG.18A. When pivoted radially about deployment catheter 16, pivotingmembers 250 may open into a deployed configuration having distensible orexpanding membranes 252 extending over the gaps in-between the pivotingmembers 250, as shown in FIG. 188B. The distensible membrane 252 may beattached to the pivoting members 250 through various methods, e.g.,adhesives, such that when the pivoting members 250 are fully extendedinto a conical shape, the pivoting members 250 and membrane 252 form aconical shape for use as an imaging hood. The distensible membrane 252may be made out of a porous material such as a mesh or PTFE or out of atranslucent or transparent polymer such as polyurethane, PVC, Nylon,etc.

FIGS. 19A and 19B show yet another variation where the distal portion ofdeployment catheter 16 may be fabricated from a flexible metallic orpolymeric material to form a radially expanding hood 254. A plurality ofslots 256 may be formed in a uniform pattern over the distal portion ofdeployment catheter 16, as shown in FIG. 19A. The slots 256 may beformed in a pattern such that when the distal portion is urged radiallyopen, utilizing any of the methods described above, a radially expandedand conically-shaped hood 254 may be formed by each of the slots 256expanding into an opening, as shown in FIG. 19B. A distensible membrane258 may overlie the exterior surface or the interior surface of the hood254 to form a fluid-impermeable hood 254 such that the hood 254 may beutilized as an imaging hood. Alternatively, the distensible membrane 258may alternatively be formed in each opening 258 to form thefluid-impermeable hood 254. Once the imaging procedure has beencompleted, hood 254 may be retracted into its low-profile configuration.

Yet another configuration for the imaging hood may be seen in FIGS. 20Aand 20B where the imaging hood may be formed from a plurality ofoverlapping hood members 260 which overlie one another in an overlappingpattern. When expanded, each of the hood members 260 may extend radiallyoutward relative to deployment catheter 16 to form a conically-shapedimaging hood, as shown in FIG. 20B. Adjacent hood members 260 mayoverlap one another along an overlapping interface 262 to form afluid-retaining surface within the imaging hood. Moreover, the hoodmembers 260 may be made from any number of biocompatible materials,e.g., Nitinol, stainless steel, polymers, etc., which are sufficientlystrong to optionally retract surrounding tissue from the tissue regionof interest.

Although it is generally desirable to have an imaging hood contactagainst a tissue surface in a normal orientation, the imaging hood maybe alternatively configured to contact the tissue surface at an acuteangle. An imaging hood configured for such contact against tissue mayalso be especially suitable for contact against tissue surfaces havingan unpredictable or uneven anatomical geography. For instance, as shownin the variation of FIG. 21A, deployment catheter 270 may have animaging hood 272 that is configured to be especially compliant. In thisvariation, imaging hood 272 may be comprised of one or more sections 274that are configured to fold or collapse, e.g. by utilizing a pleatedsurface. Thus, as shown in FIG. 21B, when imaging hood 272 is contactedagainst uneven tissue surface T, sections 274 are able to conformclosely against the tissue. These sections 274 may be individuallycollapsible by utilizing an accordion style construction to allowconformation, e.g. to the trabeculae in the heart or the uneven anatomythat may be found inside the various body lumens.

In yet another alternative, FIG. 22A shows another variation in which animaging hood 282 is attached to deployment catheter 280. The contact lipor edge 284 may comprise one or more electrical contacts 286 positionedcircumferentially around contact edge 284. The electrical contacts 286may be configured to contact the tissue and indicate affirmativelywhether tissue contact was achieved, e.g., by measuring the differentialimpedance between blood and tissue. Alternatively, a processor, e.g.,processor 98, in electrical communication with contacts 286 may beconfigured to determine what type of tissue is in contact withelectrical contacts 286. In yet another alternative, the processor 98may be configured to measure any electrical activity that may beoccurring in the underlying tissue. e.g., accessory pathways, for thepurposes of electrically mapping the cardiac tissue and subsequentlytreating, as described below, any arrhythmias which may be detected.

Another variation for ensuring contact between imaging hood 282 and theunderlying tissue may be seen in FIG. 22B. This variation may have aninflatable contact edge 288 around the circumference of imaging hood282. The inflatable contact edge 288 may be inflated with a fluid or gasthrough inflation lumen 289 when the imaging hood 282 is to be placedagainst a tissue surface having an uneven or varied anatomy. Theinflated circumferential surface 288 may provide for continuous contactover the hood edge by conforming against the tissue surface andfacilitating imaging fluid retention within hood 282.

Aside from the imaging hood, various instrumentation may be utilizedwith the imaging and manipulation system. For instance, after the fieldwithin imaging hood 12 has been cleared of the opaque blood and theunderlying tissue is visualized through the clear fluid, blood may seepback into the imaging hood 12 and obstruct the view. One method forautomatically maintaining a clear imaging field may utilize atransducer, e.g., an ultrasonic transducer 290, positioned at the distalend of deployment catheter within the imaging hood 12, as shown in FIG.23. The transducer 290 may send an energy pulse 292 into the imaginghood 12 and wait to detect back-scattered energy 294 reflected fromdebris or blood within the imaging hood 12. If back-scattered energy isdetected, the pump may be actuated automatically to dispense more fluidinto the imaging hood until the debris or blood is no longer detected.

Alternatively, one or more sensors 300 may be positioned on the imaginghood 12 itself, as shown in FIG. 24A, to detect a number of differentparameters. For example, sensors 300 may be configured to detect for thepresence of oxygen in the surrounding blood, blood and/or imaging fluidpressure, color of the fluid within the imaging hood, etc. Fluid colormay be particularly useful in detecting the presence of blood within theimaging hood 12 by utilizing a reflective type sensor to detect backreflection from blood. Any reflected light from blood which may bepresent within imaging hood 12 may be optically or electricallytransmitted through deployment catheter 16 and to a red colored filterwithin control electronics 118. Any red color which may be detected mayindicate the presence of blood and trigger a signal to the physician orautomatically actuate the pump to dispense more fluid into the imaginghood 12 to clear the blood.

Alternative methods for detecting the presence of blood within the hood12 may include detecting transmitted light through the imaging fluidwithin imaging blood 12. If a source of white light, e.g., utilizingLEDs or optical fibers, is illuminated inside imaging hood 12, thepresence of blood may cause the color red to be filtered through thisfluid. The degree or intensity of the red color detected may correspondto the amount of blood present within imaging hood 12. A red colorsensor can simply comprise, in one variation, a phototransistor with ared transmitting filter over it which can establish how much red lightis detected, which in turn can indicate the presence of blood withinimaging hood 12. Once blood is detected, the system may pump moreclearing fluid through and enable closed loop feedback control of theclearing fluid pressure and flow level.

Any number of sensors may be positioned along the exterior 302 ofimaging hood 12 or within the interior 304 of imaging hood 12 to detectparameters not only exteriorly to imaging hood 12 but also withinimaging hood 12. Such a configuration, as shown in FIG. 24B, may beparticularly useful for automatically maintaining a clear imaging fieldbased upon physical parameters such as blood pressure, as describedabove for FIGS. 10A and 10B.

Aside from sensors, one or more light emitting diodes (LEDs) may beutilized to provide lighting within the imaging hood 12. Althoughillumination may be provided by optical fibers routed through deploymentcatheter 16, the use of LEDs over the imaging hood 12 may eliminate theneed for additional optical fibers for providing illumination. Theelectrical wires connected to the one or more LEDs may be routed throughor over the hood 12 and along an exterior surface or extruded withindeployment catheter 16. One or more LEDs may be positioned in acircumferential pattern 306 around imaging hood 12, as shown in FIG.25A, or in a linear longitudinal pattern 308 along imaging hood 12, asshown in FIG. 25B. Other patterns, such as a helical or spiral pattern,may also be utilized. Alternatively, LEDs may be positioned along asupport member forming part of imaging hood 12.

In another alternative for illumination within imaging hood 12, aseparate illumination tool 310 may be utilized, as shown in FIG. 26A. Anexample of such a tool may comprise a flexible intravascular deliverymember 312 having a carrier member 314 pivotably connected 316 to adistal end of delivery member 312. One or more LEDs 318 may be mountedalong carrier member 314. In use, delivery member 312 may be advancedthrough deployment catheter 16 until carrier member 314 is positionedwithin imaging hood 12. Once within imaging hood 12, carrier member 314may be pivoted in any number of directions to facilitate or optimize theillumination within the imaging hood 12, as shown in FIG. 26B.

In utilizing LEDs for illumination, whether positioned along imaginghood 12 or along a separate instrument, the LEDs may comprise a singleLED color, e.g., white light. Alternatively, LEDs of other colors, e.g.,red, blue, yellow, etc., may be utilized exclusively or in combinationwith white LEDs to provide for varied illumination of the tissue orfluids being imaged. Alternatively, sources of infrared or ultravioletlight may be employed to enable imaging beneath the tissue surface orcause fluorescence of tissue for use in system guidance, diagnosis, ortherapy.

Aside from providing a visualization platform, the imaging assembly mayalso be utilized to provide a therapeutic platform for treating tissuebeing visualized. As shown in FIG. 27, deployment catheter 320 may haveimaging hood 322, as described above, and fluid delivery lumen 324 andimaging lumen 326. In this variation, a therapeutic tool such as needle328 may be delivered through fluid delivery lumen 324 or in anotherworking lumen and advanced through open area 332 for treating the tissuewhich is visualized. In this instance, needle 328 may define one orseveral ports 330 for delivering drugs therethrough. Thus, once theappropriate region of tissue has been imaged and located, needle 328 maybe advanced and pierced into the underlying tissue where a therapeuticagent may be delivered through ports 330. Alternatively, needle 328 maybe in electrical communication with a power source 334, e.g.,radio-frequency, microwave, etc., for ablating the underlying tissuearea of interest.

FIG. 28 shows another alternative in which deployment catheter 340 mayhave imaging hood 342 attached thereto, as above, but with a therapeutictool 344 in the configuration of a helical tissue piercing device 344.Also shown and described above in FIGS. 7A and 7B for use in stabilizingthe imaging hood relative to the underlying tissue, the helical tissuepiercing device 344 may also be utilized to manipulate the tissue for avariety of therapeutic procedures. The helical portion 346 may alsodefine one or several ports for delivery of therapeutic agentstherethrough.

In yet another alternative, FIG. 29 shows a deployment catheter 350having an expandable imaging balloon 352 filled with, e.g., saline 356.A therapeutic tool 344, as above, may be translatable relative toballoon 352. To prevent the piercing portion 346 of the tool fromtearing balloon 352, a stop 354 may be formed on balloon 352 to preventthe proximal passage of portion 346 past stop 354.

Alternative configurations for tools which may be delivered throughdeployment catheter 16 for use in tissue manipulation within imaginghood 12 are shown in FIGS. 30A and 30B. FIG. 30A shows one variation ofan angled instrument 360, such as a tissue grasper, which may beconfigured to have an elongate shaft for intravascular delivery throughdeployment catheter 16 with a distal end which may be angled relative toits elongate shaft upon deployment into imaging hood 12. The elongateshaft may be configured to angle itself automatically, e.g., by theelongate shaft being made at least partially from a shape memory alloy,or upon actuation. e.g., by tensioning a pullwire. FIG. 30B showsanother configuration for an instrument 362 being configured toreconfigure its distal portion into an off-axis configuration withinimaging hood 12. In either case, the instruments 360, 362 may bereconfigured into a low-profile shape upon withdrawing them proximallyback into deployment catheter 16.

Other instruments or tools which may be utilized with the imaging systemis shown in the side and end views of FIGS. 31A to 31C. FIG. 31A shows aprobe 370 having a distal end effector 372, which may be reconfiguredfrom a low-profile shape to a curved profile. The end effector 372 maybe configured as an ablation probe utilizing radio-frequency energy,microwave energy, ultrasound energy, laser energy or even cryo-ablation.Alternatively, the end effector 372 may have several electrodes upon itfor detecting or mapping electrical signals transmitted through theunderlying tissue.

In the case of an end effector 372 utilized for ablation of theunderlying tissue, an additional temperature sensor such as athermocouple or thermistor 374 positioned upon an elongate member 376may be advanced into the imaging hood 12 adjacent to the distal endeffector 372 for contacting and monitoring a temperature of the ablatedtissue. FIG. 31B shows an example in the end view of one configurationfor the distal end effector 372 which may be simply angled into aperpendicular configuration for contacting the tissue. FIG. 31C showsanother example where the end effector may be reconfigured into a curvedend effector 378 for increased tissue contact.

FIGS. 32A and 32B show another variation of an ablation tool utilizedwith an imaging hood 12 having an enclosed bottom portion. In thisvariation, an ablation probe, such as a cryo-ablation probe 380 having adistal end effector 382, may be positioned through the imaging hood 12such that the end effector 382 is placed distally of a transparentmembrane or enclosure 384, as shown in the end view of FIG. 32B. Theshaft of probe 380 may pass through an opening 386 defined through themembrane 384. In use, the clear fluid may be pumped into imaging hood12, as described above, and the distal end effector 382 may be placedagainst a tissue region to be ablated with the imaging hood 12 and themembrane 384 positioned atop or adjacent to the ablated tissue. In thecase of cryo-ablation, the imaging fluid may be warmed prior todispensing into the imaging hood 12 such that the tissue contacted bythe membrane 384 may be warmed during the cryo-ablation procedure. Inthe case of thermal ablation, e.g., utilizing radio-frequency energy,the fluid dispensed into the imaging hood 12 may be cooled such that thetissue contacted by the membrane 384 and adjacent to the ablation probeduring the ablation procedure is likewise cooled.

In either example described above, the imaging fluid may be varied inits temperature to facilitate various procedures to be performed uponthe tissue. In other cases, the imaging fluid itself may be altered tofacilitate various procedures. For instance as shown in FIG. 33A, adeployment catheter 16 and imaging hood 12 may be advanced within ahollow body organ, such as a bladder filled with urine 394, towards alesion or tumor 392 on the bladder wall. The imaging hood 12 may beplaced entirely over the lesion 392, or over a portion of the lesion.Once secured against the tissue wall 390, a cryo-fluid, i.e., a fluidwhich has been cooled to below freezing temperatures of, e.g., water orblood, may be pumped into the imaging hood 12 to cryo-ablate the lesion390, as shown in FIG. 33B while avoiding the creation of ice on theinstrument or surface of tissue.

As the cryo-fluid leaks out of the imaging hood 12 and into the organ,the fluid may be warmed naturally by the patient body and ultimatelyremoved. The cryo-fluid may be a colorless and translucent fluid whichenables visualization therethrough of the underlying tissue. An exampleof such a fluid is Fluorinert™ (3M, St. Paul, Minn.), which is acolorless and odorless perfluorinated liquid. The use of a liquid suchas Fluorinert™ enables the cryo-ablation procedure without the formationof ice within or outside of the imaging hood 12. Alternatively, ratherthan utilizing cryo-ablation, hyperthermic treatments may also beeffected by heating the Fluorinert™ liquid to elevated temperatures forablating the lesion 392 within the imaging hood 12. Moreover,Fluorinert™ may be utilized in various other parts of the body, such aswithin the heart.

FIG. 34A shows another variation of an instrument which may be utilizedwith the imaging system. In this variation, a laser ring generator 400may be passed through the deployment catheter 16 and partially intoimaging hood 12. A laser ring generator 400 is typically used to createa circular ring of laser energy 402 for generating a conduction blockaround the pulmonary veins typically in the treatment of atrialfibrillation. The circular ring of laser energy 402 may be generatedsuch that a diameter of the ring 402 is contained within a diameter ofthe imaging hood 12 to allow for tissue ablation directly upon tissuebeing imaged. Signals which cause atrial fibrillation typically comefrom the entry area of the pulmonary veins into the left atrium andtreatments may sometimes include delivering ablation energy to the ostiaof the pulmonary veins within the atrium. The ablated areas of thetissue may produce a circular scar which blocks the impulses for atrialfibrillation.

When using the laser energy to ablate the tissue of the heart, it may begenerally desirable to maintain the integrity and health of the tissueoverlying the surface while ablating the underlying tissue. This may beaccomplished, for example, by cooling the imaging fluid to a temperaturebelow the body temperature of the patient but which is above thefreezing point of blood (e.g., 2.degree. C. to 35.degree. C.). Thecooled imaging fluid may thus maintain the surface tissue at the cooledfluid temperature while the deeper underlying tissue remains at thepatient body temperature. When the laser energy (or other types ofenergy such as radio frequency energy, microwave energy, ultrasoundenergy, etc.) irradiates the tissue, both the cooled tissue surface aswell as the deeper underlying tissue will rise in temperature uniformly.The deeper underlying tissue, which was maintained at the bodytemperature, will increase to temperatures which are sufficiently highto destroy the underlying tissue. Meanwhile, the temperature of thecooled surface tissue will also rise but only to temperatures that arenear body temperature or slightly above.

Accordingly, as shown in FIG. 34B, one example for treatment may includepassing deployment catheter 16 across the atrial septum AS and into theleft atrium LA of the patient's heart H. Other methods of accessing theleft atrium LA may also be utilized. The imaging hood 12 and laser ringgenerator 400 may be positioned adjacent to or over one or more of theostium OT of the pulmonary veins PV and the laser generator 400 mayablate the tissue around the ostium OT with the circular ring of laserenergy 402 to create a conduction block. Once one or more of the tissuearound the ostium OT have been ablated, the imaging hood 12 may bereconfigured into a low profile for removal from the patient heart H.

One of the difficulties in treating tissue in or around the ostium OT isthe dynamic fluid flow of blood through the ostium OT. The dynamicforces make cannulation or entry of the ostium OT difficult. Thus,another variation on instruments or tools utilizable with the imagingsystem is an extendible cannula 410 having a cannula lumen 412 definedtherethrough, as shown in FIG. 35A. The extendible cannula 410 maygenerally comprise an elongate tubular member which may be positionedwithin the deployment catheter 16 during delivery and then projecteddistally through the imaging hood 12 and optionally beyond, as shown inFIG. 35B.

In use, once the imaging hood 12 has been desirably positioned relativeto the tissue, e.g., as shown in FIG. 35C outside the ostium OT of apulmonary vein PV, the extendible cannula 410 may be projected distallyfrom the deployment catheter 16 while optionally imaging the tissuethrough the imaging hood 12, as described above. The extendible cannula410 may be projected distally until its distal end is extended at leastpartially into the ostium OT. Once in the ostium OT, an instrument orenergy ablation device may be extended through and out of the cannulalumen 412 for treatment within the ostium OT. Upon completion of theprocedure, the cannula 410 may be withdrawn proximally and removed fromthe patient body. The extendible cannula 410 may also include aninflatable occlusion balloon at or near its distal end to block theblood flow out of the PV to maintain a clear view of the tissue region.Alternatively, the extendible cannula 410 may define a lumentherethrough beyond the occlusion balloon to bypass at least a portionof the blood that normally exits the pulmonary vein PV by directing theblood through the cannula 410 to exit proximal of the imaging hood.

Yet another variation for tool or instrument use may be seen in the sideand end views of FIGS. 36A and 36B. In this variation, imaging hood 12may have one or more tubular support members 420 integrated with thehood 12. Each of the tubular support members 420 may define an accesslumen 422 through which one or more instruments or tools may bedelivered for treatment upon the underlying tissue. One particularexample is shown and described above for FIG. 7C.

Various methods and instruments may be utilized for using orfacilitating the use of the system. For instance, one method may includefacilitating the initial delivery and placement of a device into thepatient's heart. In initially guiding the imaging assembly within theheart chamber to, e.g., the mitral valve MV, a separate guiding probe430 may be utilized, as shown in FIGS. 37A and 37B. Guiding probe 430may, for example, comprise an optical fiber through which a light source434 may be used to illuminate a distal tip portion 432. The tip portion432 may be advanced into the heart through, e.g., the coronary sinus CS,until the tip is positioned adjacent to the mitral valve MV. The tip 432may be illuminated, as shown in FIG. 37A, and imaging assembly 10 maythen be guided towards the illuminated tip 432, which is visible fromwithin the atrial chamber, towards mitral valve MV.

Aside from the devices and methods described above, the imaging systemmay be utilized to facilitate various other procedures. Turning now toFIGS. 38A and 38B, the imaging hood of the device in particular may beutilized. In this example, a collapsible membrane or disk-shaped member440 may be temporarily secured around the contact edge or lip of imaginghood 12. During intravascular delivery, the imaging hood 12 and theattached member 440 may both be in a collapsed configuration to maintaina low profile for delivery. Upon deployment, both the imaging hood 12and the member 440 may extend into their expanded configurations.

The disk-shaped member 440 may be comprised of a variety of materialsdepending upon the application. For instance, member 440 may befabricated from a porous polymeric material infused with a drug elutingmedicament 442 for implantation against a tissue surface for slowinfusion of the medicament into the underlying tissue. Alternatively,the member 440 may be fabricated from a non-porous material, e.g., metalor polymer, for implantation and closure of a wound or over a cavity toprevent fluid leakage. In yet another alternative, the member 440 may bemade from a distensible material which is secured to imaging hood 12 inan expanded condition. Once implanted or secured on a tissue surface orwound, the expanded member 440 may be released from imaging hood 12.Upon release, the expanded member 440 may shrink to a smaller size whileapproximating the attached underlying tissue, e.g., to close a wound oropening.

One method for securing the disk-shaped member 440 to a tissue surfacemay include a plurality of tissue anchors 444, e.g., barbs, hooks,projections, etc., which are attached to a surface of the member 440.Other methods of attachments may include adhesives, suturing, etc. Inuse, as shown in FIGS. 39A to 39C, the imaging hood 12 may be deployedin its expanded configuration with member 440 attached thereto with theplurality of tissue anchors 444 projecting distally. The tissue anchors444 may be urged into a tissue region to be treated 446, as seen in FIG.39A, until the anchors 444 are secured in the tissue and member 440 ispositioned directly against the tissue, as shown in FIG. 39B. A pullwiremay be actuated to release the member 440 from the imaging hood 12 anddeployment catheter 16 may be withdrawn proximally to leave member 440secured against the tissue 446.

Another variation for tissue manipulation and treatment may be seen inthe variation of FIG. 40A, which illustrates an imaging hood 12 having adeployable anchor assembly 450 attached to the tissue contact edge 22.FIG. 40B illustrates the anchor assembly 450 detached from the imaginghood 12 for clarity. The anchor assembly 450 may be seen as having aplurality of discrete tissue anchors 456, e.g., barbs, hooks,projections, etc., each having a suture retaining end, e.g., an eyeletor opening 458 in a proximal end of the anchors 456. A suture member orwire 452 may be slidingly connected to each anchor 456 through theopenings 458 and through a cinching element 454, which may be configuredto slide uni-directionally over the suture or wire 452 to approximateeach of the anchors 456 towards one another. Each of the anchors 456 maybe temporarily attached to the imaging hood 12 through a variety ofmethods. For instance, a pullwire or retaining wire may hold each of theanchors within a receiving ring around the circumference of the imaginghood 12. When the anchors 456 are released, the pullwire or retainingwire may be tensioned from its proximal end outside the patient body tothereby free the anchors 456 from the imaging hood 12.

One example for use of the anchor assembly 450 is shown in FIGS. 41A to41D for closure of an opening or wound 460, e.g., patent foramen ovale(PFO). The deployment catheter 16 and imaging hood 12 may be deliveredintravascularly into, e.g., a patient heart. As the imaging hood 12 isdeployed into its expanded configuration, the imaging hood 12 may bepositioned adjacent to the opening or wound 460, as shown in FIG. 41A.With the anchor assembly 450 positioned upon the expanded imaging hood12, deployment catheter 16 may be directed to urge the contact edge ofimaging hood 12 and anchor assembly 450 into the region surrounding thetissue opening 460, as shown in FIG. 41B. Once the anchor assembly 450has been secured within the surrounding tissue, the anchors may bereleased from imaging hood 12 leaving the anchor assembly 450 and suturemember 452 trailing from the anchors, as shown in FIG. 41C. The sutureor wire member 452 may be tightened by pulling it proximally fromoutside the patient body to approximate the anchors of anchor assembly450 towards one another in a purse-string manner to close the tissueopening 462, as shown in FIG. 41D. The cinching element 454 may also bepushed distally over the suture or wire member 452 to prevent theapproximated anchor assembly 450 from loosening or widening.

Another example for an alternative use is shown in FIG. 42, where thedeployment catheter 16 and deployed imaging hood 12 may be positionedwithin a patient body for drawing blood 472 into deployment catheter 16.The drawn blood 472 may be pumped through a dialysis unit 470 locatedexternally of the patient body for filtering the drawn blood 472 and thefiltered blood may be reintroduced back into the patient.

Yet another variation is shown in FIGS. 43A and 43B, which show avariation of the deployment catheter 480 having a first deployable hood482 and a second deployable hood 484 positioned distal to the first hood482. The deployment catheter 480 may also have a side-viewing imagingelement 486 positioned between the first and second hoods 482, 484 alongthe length of the deployment catheter 480. In use, such a device may beintroduced through a lumen 488 of a vessel VS, where one or both hoods482, 484 may be expanded to gently contact the surrounding walls ofvessel VS. Once hoods 482, 484 have been expanded, the clear imagingfluid may be pumped in the space defined between the hoods 482, 484 todisplace any blood and to create an imaging space 490, as shown in FIG.43B. With the clear fluid in-between hoods 482, 484, the imaging element486 may be used to view the surrounding tissue surface contained betweenhoods 482, 484. Other instruments or tools may be passed throughdeployment catheter 480 and through one or more openings defined alongthe catheter 480 for additionally performing therapeutic procedures uponthe vessel wall.

Another variation of a deployment catheter 500 which may be used forimaging tissue to the side of the instrument may be seen in FIGS. 44A to45B. FIGS. 44A and 44B show side and end views of deployment catheter500 having a side-imaging balloon 502 in an un-inflated low-profileconfiguration. A side-imaging element 504 may be positioned within adistal portion of the catheter 500 where the balloon 502 is disposed.When balloon 502 is inflated, it may expand radially to contact thesurrounding tissue, but where the imaging element 504 is located, avisualization field 506 may be created by the balloon 502, as shown inthe side, top, and end views of FIGS. 45A to 45B, respectively. Thevisualization field 506 may simply be a cavity or channel which isdefined within the inflated balloon 502 such that the visualizationelement 504 is provided an image of the area within field 506 which isclear and unobstructed by balloon 502.

In use, deployment catheter 500 may be advanced intravascularly throughvessel lumen 488 towards a lesion or tumor 508 to be visualized and/ortreated. Upon reaching the lesion 508, deployment catheter 500 may bepositioned adjacently to the lesion 508 and balloon 502 may be inflatedsuch that the lesion 508 is contained within the visualization field506. Once balloon 502 is fully inflated and in contact against thevessel wall, clear fluid may be pumped into visualization field 506through deployment catheter 500 to displace any blood or opaque fluidsfrom the field 506, as shown in the side and end views of FIGS. 46A and46B, respectively. The lesion 508 may then be visually inspected andtreated by passing any number of instruments through deployment catheter500 and into field 506.

The applications of the disclosed invention discussed above are notlimited to certain treatments or regions of the body, but may includeany number of other treatments and areas of the body. Modification ofthe above-described methods and devices for carrying out the invention,and variations of aspects of the invention that are obvious to those ofskill in the arts are intended to be within the scope of thisdisclosure. Moreover, various combinations of aspects between examplesare also contemplated and are considered to be within the scope of thisdisclosure as well.

1. (canceled)
 2. A tissue imaging assembly comprising: a steerablesheath; and a steerable catheter deployable within the steerable sheath;and an imaging hood at a distal end of the steerable catheter, theimaging hood being independently translatable with respect to thesteerable sheath and the steerable catheter; wherein the steerablecatheter comprises: an imaging element; and a lumen for delivering anelongate instrument out a distal region of the steerable catheter. 3.The tissue imaging assembly of claim 2, wherein the elongate instrumentis a guidewire.
 4. The tissue imaging assembly of claim 2, wherein theelongate instrument is a needle.
 5. The tissue imaging assembly of claim2, wherein the elongate instrument is an electrode.
 6. The tissueimaging assembly of claim 2, wherein the imaging element comprises anoptical imaging fiber.
 7. The tissue imaging assembly of claim 6,wherein the steerable catheter further comprises an imaging lumen sizedand shaped to fit the optical imaging fiber therein.
 8. The tissueimaging assembly of claim 2, wherein the imaging hood defines an openarea.
 9. The tissue imaging assembly of claim 2, wherein the imaginghood comprises an atraumatic contact lip.
 10. The tissue imagingassembly of claim 2, wherein the lumen is concentric.
 11. The tissueimaging assembly of claim 2, wherein the lumen is eccentric.
 12. Thetissue imaging assembly of claim 2, wherein the steerable catheterfurther defines a fluid delivery lumen.
 13. A tissue imaging assemblycomprising: a steerable sheath; and a steerable catheter deployablewithin the steerable sheath, wherein the steerable catheter comprises:an imaging element; and a lumen for delivering an elongate instrumentout a distal region of the steerable catheter.
 14. The tissue imagingassembly of claim 13, wherein the elongate instrument is a guidewire.15. The tissue imaging assembly of claim 13, wherein the elongateinstrument is a needle.
 16. The tissue imaging assembly of claim 13,wherein the elongate instrument is an electrode.
 17. The tissue imagingassembly of claim 13, wherein the imaging element comprises an opticalimaging fiber.
 18. The tissue imaging assembly of claim 13, wherein thesteerable catheter further comprises an expandable hood.
 19. A methodcomprising: translating a steerable catheter with respect to a steerablesheath, the steerable catheter comprising an imaging element and a lumenfor delivering an elongate instrument out a distal region of thesteerable catheter; inserting an instrument through the lumen; andimaging a tissue region with the imaging element.
 20. The method ofclaim 19, further comprising, expanding an imaging hood that is at adistal end of the steerable catheter, the imaging hood beingindependently translatable from the steerable catheter.
 21. The methodof claim 19, wherein the lumen is a guidewire lumen and the instrumentis a guidewire.